Aircraft autopilot devices are typically engineered to control the aircraft during most typical flight operations and in more complex systems include roll and yaw stabilization, heading control, navigation control and pitch stabilization.
The pitch rate sensor, typically a rate gyro, senses the rate of pitch change (with reference to the aircraft longitudinal axis, nose-to-tail angle relative to the horizontal axis), and outputs a signal useful to generate a correction to control the pitch rate of the aircraft.
A problem is noted in that the performance of the aircraft is a function of the servos controlling the respective control surfaces of the aircraft. Their relative torque factors coupled through gearing to provide pitch rates acceptable at slower speeds, can be entirely unacceptable at higher speeds due to the excessive vertical acceleration forces on the airframe during a pitch rate command output that would otherwise be acceptable. Accordingly, the pitch rate has typically been limited by an airspeed factor input by a sensor to the autopilot. This factor reduces the allowable pitch rate command output as the aircraft speed increases.
This system works well in most instances; however, it requires an airspeed input to the autopilot so that pitch rate output can be varied accordingly.
It is an object of the present invention to provide a variably limited pitch rate command output in an aircraft to limit vertical acceleration, without requiring an airspeed input.
It is a further object of the present invention to provide a vertical acceleration limited pitch command output apparatus for an autopilot without any requirement for an airspeed sensor or airspeed compensation.